This invention relates to a ring binder mechanism for retaining loose-leaf pages, and in particular to an improved mechanism for opening and closing ring members and for readily and securely locking ring members together.
As is known in the art, a typical ring binder mechanism retains loose-leaf pages, such as hole-punched papers, in a file or notebook. It generally features multiple rings each including two half ring members capable of selectively opening to add or remove pages, or selectively closing to retain pages and allow them to move along the ring members. The ring members mount on two adjacent hinge plates that join together about a pivot axis for pivoting movement within an elongated housing. The housing loosely holds the hinge plates so they may pivot relative to the housing. The undeformed housing is slightly narrower than the joined hinge plates when the hinge plates are in a coplanar position (180°). So as the hinge plates pivot through this position, they deform the resilient housing and cause a spring force in the housing urging the hinge plates to pivot away from the coplanar position either opening or closing the ring members. Thus, when the ring members are closed the spring force resists hinge plate movement and clamps the ring members together. Similarly, when the ring members are open, the spring force holds them apart. An operator may typically overcome this force by manually pulling the ring members apart or pushing them together. In addition, in some mechanisms the operator may move a lever located at one or both ends of the mechanism for moving the hinge plates through the coplanar position to open or close the ring members (in addition to manually pulling the ring members apart or pushing them together).
One drawback to these typical ring binder mechanisms is that when the ring members close, the housing's spring force snaps them together rapidly and with a force that might cause fingers to be pinched between the ring members. The substantial spring force required to keep the ring members closed also makes pivoting the hinge plates through the coplanar position (180°) difficult so that it is hard to both open and close the ring members. Another drawback is that when the ring members are closed, they do not positively lock together. So if the mechanism is accidentally dropped, the ring members may unintentionally open. Still another drawback is that over time the housing may begin to permanently deform, reducing its ability to uniformly clamp the ring members together and possibly causing uneven movements or gaps between closed ring members.
To address these concerns, some ring binder mechanisms include a control slide attached directly to the lever. These control slides have inclined cam surfaces that project through openings in the hinge plates for rigidly controlling the hinge plates' pivoting motion both when opening and closing the ring members. Examples of these types of mechanisms are shown in U.S. Pat. Nos. 4,566,817, 4,571,108, and 6,276,862 and in U.K. Pat. No. 2,292,343. Some of these cam surfaces have a stop for blocking the hinge plates' pivoting motion when the ring members are closed and for locking the closed ring members together. An operator may open or close these mechanisms by either manipulating the ring members or moving the lever. But to lock the mechanisms, the operator must move the lever and the control slide to position the stops to block the hinge plates from pivoting.
These mechanisms still have several drawbacks. When the ring members close, the housing's spring force may still snap them together. The spring force may also still make both opening and closing the ring members difficult. In addition, when the mechanisms close they do not readily lock. Instead, an operator must directly move the lever and control slide to lock the mechanisms. Furthermore, the control slides in these mechanisms, specifically their inclined cam surfaces and stops, are complexly shaped and can be difficult and time consuming to fabricate. Moreover, since the control slides directly bias the hinge plates, they are usually relatively wide and may need to be constructed of a large gauge metal to withstand forces associated with repeated use (i.e., repeatedly driving the hinge plates to pivot). Therefore, the openings in the hinge plates receiving these control slides may also be relatively wide, possibly weakening the hinge plates so that they too must be made of a large gauge metal. This may make mass production more costly.
Consequently, there is a need for a ring binder mechanism that readily locks when ring members close for retaining loose-leaf pages, but has ring members that easily open and close and do not snap together. The present invention is directed to such a ring binder mechanism.